Luxembourg Research Evaluation 2022: Field Mapping of Knowledge Structure

# Introduction:

Department

Here are preliminary results of the bibliometric mapping of the 2022 Luxembourg research evaluation. Its purpose is:

• To map the broader research community and distinct research field the department contributes to.
• Identify core knowledge bases, research areas gtrends and topics.
• Highlight the positioning of the department within this dynamics.

The method for the research-field-mapping can be reiviewed here:

Rakas, M., & Hain, D. S. (2019). The state of innovation system research: What happens beneath the surface?. Research Policy, 48(9), 103787.

Seed Articles

The seed articles deemed representative for the active areas of research in the institution, and include authors affiliated with the institution. They can be selected in three ways:

1. Via bibliographic clustering of the institutions publications and selection of most central articles per cluster (only clsuters where n >= 0.05N). Selection can be found at:https://github.com/daniel-hain/biblio_lux_2022/blob/master/output/seed/scopus_list_mrt_seed.csv
2. MAnual selection of relevant publications.
3. A combination of 1. and 2.

The present analysis is based on the following seed articles:

AU	PY	TI	JI
BENGASI G;DESPORT JS;BABA K…	2020	MOLECULAR FLATTENING EFFECT TO ENHANCE THE CONDUCTIVITY OF FUSED PORPHYRIN TAPE THIN FILMS	RSC ADV.
ZHAO HJ;ÍÑIGUEZ J	2019	CREATING MULTIFERROIC AND CONDUCTIVE DOMAIN WALLS IN COMMON FERROELASTIC COMPOUNDS	NPJ COMPUTATIONAL MATER.
CHEN P;GRISOLIA MN;ZHAO HJ;…	2018	ENERGETICS OF OXYGEN-OCTAHEDRA ROTATIONS IN PEROVSKITE OXIDES FROM FIRST PRINCIPLES	PHYS. REV. B
GIUNTA G;DE PIETRO G;NASSER…	2016	A THERMAL STRESS FINITE ELEMENT ANALYSIS OF BEAM STRUCTURES BY HIERARCHICAL MODELLING	COMPOS PART B: ENG

Topic modelling

Here, we report the results of a LDA topic-modelling (basically, clustering on words) on all title+abstract texts.

Topics by topwords

Note: While this static vies is helpful, I recommend using the interactive LDAVis version to be found under https://daniel-hain.github.io/biblio_lux_2022/output/topic_modelling/LDAviz_list_mrt.rds/index.html#topic=1&lambda=0.60&term=. For functionality and usage, see technical description in the next tab.

Topics over time

Technical Description

LDA Topic Modelling

Topic modeling is a type of statistical modeling for discovering the abstract “topics” that occur in a collection of documents. Latent Dirichlet Allocation (LDA) is an example of topic model and is used to classify text in a document to a particular topic.

LDA is a generative probabilistic model that assumes each topic is a mixture over an underlying set of words, and each document is a mixture of over a set of topic probabilities. It builds a topic per document model and words per topic model, modeled as Dirichlet distributions.

LDAVis

LDAvis is a web-based interactive visualisation of topics estimated using LDA. It provides a global view of the topics (and how they differ from each other), while at the same time allowing for a deep inspection of the terms most highly associated with each individual topic. The package extracts information from a fitted LDA topic model to inform an interactive web-based visualization. The visualisation has two basic pieces.

The left panel visualise the topics as circles in the two-dimensional plane whose centres are determined by computing the Jensen–Shannon divergence between topics, and then by using multidimensional scaling to project the inter-topic distances onto two dimensions. Each topic’s overall prevalence is encoded using the areas of the circles.

The right panel depicts a horizontal bar chart whose bars represent the individual terms that are the most useful for interpreting the currently selected topic on the left. A pair of overlaid bars represent both the corpus-wide frequency of a given term as well as the topic-specific frequency of the term.

The \(\lambda\) slider allows to rank the terms according to term relevance. By default, the terms of a topic are ranked in decreasing order according their topic-specific probability ( \(\lambda\) = 1 ). Moving the slider allows to adjust the rank of terms based on much discriminatory (or “relevant”) are for the specific topic. The suggested optimal value of \(\lambda\) is 0.6.

Knowledge Bases: Co-Citation network analysis

Note: This analysis refers the co-citation analysis, where the cited references and not the original publications are the unit of analysis. See tab Technical descriptionfor additional explanations

Knowledge Bases summary

In order to partition networks into components or clusters, we deploy a community detection technique based on the Lovain Algorithm (Blondel et al., 2008). The Lovain Algorithm is a heuristic method that attempts to optimize the modularity of communities within a network by maximizing within- and minimizing between-community connectivity. We identify the following communities = knowledge bases.

com	name	dgr_int	dgr
Knowledge Base 1: KB 1 (n = 1821, density =4.6)
1	KRESSE G. FURTHMÜLLER J. (1996)	10244	10264
1	KRESSE G. JOUBERT D. (1999)	9931	9955
1	BLÖCHL P.E. (1994)	8758	8780
1	PERDEW J.P. BURKE K. ERNZERHOF M. (1996)	7380	7440
1	PERDEW J.P. RUZSINSZKY A. CSONKA G.I. VYDROV O.A. SCUSERIA G.E. CONSTANTIN L.A. ZHOU X. BURKE K. (2008)	3878	3888
1	DUDAREV S.L. BOTTON G.A. SAVRASOV S.Y. HUMPHREYS C.J. SUTTON A.P. (1998)	3694	3697
1	KRESSE G. HAFNER J. (1993)	3658	3658
1	MOMMA K. IZUMI F. (2011)	3166	3169
1	MONKHORST H.J. PACK J.D. (1976)	3011	3017
1	HOHENBERG P. KOHN W. (1964)	2855	2872
Knowledge Base 2: KB 2 (n = 1218, density =6.35)
2	BLÖCHL P.E. PROJECTOR AUGMENTED-WAVE METHOD (1994)	7255	7312
2	KRESSE G. JOUBERT D. FROM ULTRASOFT PSEUDOPOTENTIALS TO THE PROJECTOR AUGMENTED-WAVE METHOD (1999)	7187	7236
2	KRESSE G. FURTHMÜLLER J. EFFICIENT ITERATIVE SCHEMES FOR AB INITIO TOTAL-ENERGY CALCULATIONS USING A PLANE-WAVE BASIS SET (1996)	6661	6709
2	PERDEW J.P. BURKE K. ERNZERHOF M. GENERALIZED GRADIENT APPROXIMATION MADE SIMPLE (1996)	5640	5744
2	KRESSE G. FURTHMÜLLER J. EFFICIENCY OF AB-INITIO TOTAL ENERGY CALCULATIONS FOR METALS AND SEMICONDUCTORS USING A PLANE-WAVE BASIS SET (1996)	2882	2898
2	KRESSE G. HAFNER J. AB INITIO MOLECULAR DYNAMICS FOR LIQUID METALS (1993)	2297	2303
2	MONKHORST H.J. PACK J.D. SPECIAL POINTS FOR BRILLOUIN-ZONE INTEGRATIONS (1976)	2187	2193
2	MOMMA K. IZUMI F. VESTA 3 FOR THREE-DIMENSIONAL VISUALIZATION OF CRYSTAL VOLUMETRIC AND MORPHOLOGY DATA (2011)	2125	2138
2	KOHN W. SHAM L.J. SELF-CONSISTENT EQUATIONS INCLUDING EXCHANGE AND CORRELATION EFFECTS (1965)	1986	1993
2	DUDAREV S.L. BOTTON G.A. SAVRASOV S.Y. HUMPHREYS C.J. SUTTON A.P. ELECTRON-ENERGY-LOSS SPECTRA AND THE STRUCTURAL STABILITY OF NICKEL OXIDE: AN LSD…	1865	1872
Knowledge Base 3: KB 3 (n = 739, density =9.47)
3	CARRERA E. THEORIES AND FINITE ELEMENTS FOR MULTILAYERED PLATES AND SHELLS: A UNIFIED COMPACT FORMULATION WITH NUMERICAL ASSESSMENT AND BENCHMARKIN…	2194	2194
3	CARRERA E. THEORIES AND FINITE ELEMENTS FOR MULTILAYERED ANISOTROPIC COMPOSITE PLATES AND SHELLS (2002)	1176	1176
3	CARRERA E. PETROLO M. REFINED BEAM ELEMENTS WITH ONLY DISPLACEMENT VARIABLES AND PLATE/SHELL CAPABILITIES (2012)	899	899
3	CARRERA E. CINEFRA M. PETROLO M. ZAPPINO E. FINITE ELEMENT ANALYSIS OF STRUCTURES THROUGH UNIFIED FORMULATION (2014)	787	787
3	CARRERA E. GIUNTA G. PETROLO M. (2011)	785	785
3	CARRERA E. HISTORICAL REVIEW OF ZIG-ZAG THEORIES FOR MULTILAYERED PLATES AND SHELLS (2003)	633	633
3	CARRERA E. GIUNTA G. NALI P. PETROLO M. REFINED BEAM ELEMENTS WITH ARBITRARY CROSS-SECTION GEOMETRIES (2010)	620	620
3	CARRERA E. GIUNTA G. PETROLO M. BEAM STRUCTURES: CLASSICAL AND ADVANCED THEORIES (2011)	608	608
3	CARRERA E. CINEFRA M. PETROLO M. ZAPPINO E. (2014)	585	585
3	REISSNER E. THE EFFECT OF TRANSVERSE SHEAR DEFORMATION ON THE BENDING OF ELASTIC PLATES (1945)	578	578
Knowledge Base 4: KB 4 (n = 583, density =6.53)
4	TANAKA T. OSUKA A. (2015)	770	815
4	ETHIRAJAN M. CHEN Y. JOSHI P. PANDEY R.K. (2011)	759	851
4	TSUDA A. OSUKA A. (2001)	742	758
4	MORI H. TANAKA T. OSUKA A. (2013)	629	641
4	LEWTAK J.P. GRYKO D.T. (2012)	516	522
4	GRZYBOWSKI M. SKONIECZNY K. BUTENSCHÖN H. GRYKO D.T. (2013)	395	395
4	ARATANI N. KIM D. OSUKA A. (2009)	362	368
4	FOX S. BOYLE R.W. (2006)	345	345
4	DAVIS N.K.S. THOMPSON A.L. ANDERSON H.L. (2011)	328	334
4	ANDERSON H.L. (1999)	316	343
Knowledge Base 5: KB 5 (n = 466, density =15.06)
5	O’REGAN B. GRÄTZEL M. (1991)	1366	1378
5	HIGASHINO T. IMAHORI H. (2015)	1256	1311
5	HAGFELDT A. BOSCHLOO G. SUN L. KLOO L. PETTERSSON H. (2010)	1225	1231
5	MATHEW S. YELLA A. GAO P. HUMPHRY-BAKER R. CURCHOD B.F.E. ASHARI-ASTANI N. TAVERNELLI I. GRÄTZEL M. (2014)	1115	1219
5	LI L.-L. DIAU E.W.-G. (2013)	1067	1230
5	URBANI M. GRÄTZEL M. NAZEERUDDIN M.K. TORRES T. (2014)	1058	1115
5	IMAHORI H. UMEYAMA T. ITO S. (2009)	975	991
5	YELLA A. LEE H.-W. TSAO H.N. YI C. CHANDIRAN A.K. NAZEERUDDIN M.K. DIAU E.W.-G. GRÄTZEL M. (2011)	867	889
5	YELLA A. MAI C.-L. ZAKEERUDDIN S.M. CHANG S.-N. HSIEH C.-H. YEH C.-Y. GRÄTZEL M. (2014)	624	627
5	MISHRA A. FISCHER M.K.R. BÄUERLE P. (2009)	465	465
Knowledge Base 6: KB 6 (n = 443, density =7.8)
6	LI L.-L. DIAU E.W.-G. PORPHYRIN-SENSITIZED SOLAR CELLS (2013)	729	741
6	HAGFELDT A. BOSCHLOO G. SUN L. KLOO L. PETTERSSON H. DYE-SENSITIZED SOLAR CELLS (2010)	662	670
6	URBANI M. GRÄTZEL M. NAZEERUDDIN M.K. TORRES T. MESO-SUBSTITUTED PORPHYRINS FOR DYE-SENSITIZED SOLAR CELLS (2014)	615	619
6	MATHEW S. YELLA A. GAO P. HUMPHRY-BAKER R. CURCHOD B.F.E. ASHARI-ASTANI N. TAVERNELLI I. GRÄTZEL M. DYE-SENSITIZED SOLAR CELLS WITH 13% EFFICIENCY …	592	597
6	O’REGAN B. GRÄTZEL M. A LOW-COST HIGH-EFFICIENCY SOLAR CELL BASED ON DYE-SENSITIZED COLLOIDAL TIO2 FILMS (1991)	523	531
6	ETHIRAJAN M. CHEN Y. JOSHI P. PANDEY R.K. THE ROLE OF PORPHYRIN CHEMISTRY IN TUMOR IMAGING AND PHOTODYNAMIC THERAPY (2011)	503	507
6	HIGASHINO T. IMAHORI H. PORPHYRINS AS EXCELLENT DYES FOR DYE-SENSITIZED SOLAR CELLS: RECENT DEVELOPMENTS AND INSIGHTS (2015)	472	472
6	YELLA A. LEE H.-W. TSAO H.N. YI C. CHANDIRAN A.K. NAZEERUDDIN M.K. DIAU E.W.-G. GRÄTZEL M. PORPHYRIN-SENSITIZED SOLAR CELLS WITH COBALT (II/III)	337	337
6	YAO Z. ZHANG M. WU H. YANG L. LI R. WANG P. DONOR/ACCEPTOR INDENOPERYLENE DYE FOR HIGHLY EFFICIENT ORGANIC DYE-SENSITIZED SOLAR CELLS (2015)	226	226
6	SONG H. LIU Q. XIE Y. PORPHYRIN-SENSITIZED SOLAR CELLS: SYSTEMATIC MOLECULAR OPTIMIZATION COADSORPTION AND COSENSITIZATION (2018)	193	196

Development of Knowledge Bases

Technical description

In a co-cittion network, the strength of the relationship between a reference pair \(m\) and \(n\) (\(s_{m,n}^{coc}\)) is expressed by the number of publications \(C\) which are jointly citing reference \(m\) and \(n\).

\[s_{m,n}^{coc} = \sum_i c_{i,m} c_{i,n}\]

The intuition here is that references which are frequently cited together are likely to share commonalities in theory, topic, methodology, or context. It can be interpreted as a measure of similarity as evaluated by other researchers that decide to jointly cite both references. Because the publication process is time-consuming, co-citation is a backward-looking measure, which is appropriate to map the relationship between core literature of a field.

Research Areas: Bibliographic coupling analysis

Research Areas main summary

This is arguably the more interesting part. Here, we identify the literature’s current knowledge frontier by carrying out a bibliographic coupling analysis of the publications in our corpus. This measure uses bibliographical information of publications to establish a similarity relationship between them. Again, method details to be found in the tab Technical description. As you will see, we identify the main research area, but also a set of adjacent research areas with some theoretical/methodological/application overlap.

To identify communities in the field’s knowledge frontier (labeled research areas) we again use the Lovain Algorithm (Blondel et al., 2008). We identify the following communities = research areas.

com_name	AU	PY	TI	dgr_int	TC	TC_year
Research Area 1: RA 1 (n = 1140, density =2.1)
RA 1	WANG Z;GRESCH D;SOLUYA…	2016	MOTE2: A TYPE-II WEYL TOPOLOGICAL METAL	32.6758154	318	53.000000
RA 1	HINUMA Y;PIZZI G;KUMAG…	2017	BAND STRUCTURE DIAGRAM PATHS BASED ON CRYSTALLOGRAPHY	39.9129643	256	51.200000
RA 1	OTROKOV MM;RUSINOV IP;…	2019	UNIQUE THICKNESS-DEPENDENT PROPERTIES OF THE VAN DER WAALS INTERLAYER ANTIFERROMAGNET MNBI2TE4 FILMS	31.1020458	235	78.333333
RA 1	QIAO J;NING L;MOLOKEEV…	2018	EU2+ SITE PREFERENCES IN THE MIXED CATION K2BACA(PO4)2 AND THERMALLY STABLE LUMINESCENCE	24.0019278	302	75.500000
RA 1	LEE J;SEKO A;SHITARA K…	2016	PREDICTION MODEL OF BAND GAP FOR INORGANIC COMPOUNDS BY COMBINATION OF DENSITY FUNCTIONAL THEORY CALCULATIONS AND MACHINE …	38.7317584	185	30.833333
RA 1	STEINER S;KHMELEVSKYI …	2016	CALCULATION OF THE MAGNETIC ANISOTROPY WITH PROJECTED-AUGMENTED-WAVE METHODOLOGY AND THE CASE STUDY OF DISORDERED FE1-XCOX…	37.4671718	189	31.500000
RA 1	KYRTSOS A;MATSUBARA M;…	2018	ON THE FEASIBILITY OF P-TYPE GA2O3	40.8406776	151	37.750000
RA 1	MORIWAKE H;KUWABARA A;…	2017	WHY IS SODIUM-INTERCALATED GRAPHITE UNSTABLE?	44.9982805	125	25.000000
RA 1	YORULMAZ U;ÖZDEN A;PER…	2016	VIBRATIONAL AND MECHANICAL PROPERTIES OF SINGLE LAYER MXENE STRUCTURES: A FIRST-PRINCIPLES INVESTIGATION	40.5999635	138	23.000000
RA 1	SEKO A;HAYASHI H;NAKAY…	2017	REPRESENTATION OF COMPOUNDS FOR MACHINE-LEARNING PREDICTION OF PHYSICAL PROPERTIES	34.4883044	151	30.200000
Research Area 2: RA 2 (n = 999, density =2.05)
RA 2	VAN SETTEN MJ;GIANTOMA…	2018	THE PSEUDODOJO: TRAINING AND GRADING A 85 ELEMENT OPTIMIZED NORM-CONSERVING PSEUDOPOTENTIAL TABLE	18.6764871	437	109.250000
RA 2	DING W;ZHU J;WANG Z;GA…	2017	PREDICTION OF INTRINSIC TWO-DIMENSIONAL FERROELECTRICS IN IN 2 SE 3 AND OTHER III 2 -VI 3 VAN DER WAALS MATERIALS	16.1845065	439	87.800000
RA 2	JI D;CAI S;PAUDEL TR;S…	2019	FREESTANDING CRYSTALLINE OXIDE PEROVSKITES DOWN TO THE MONOLAYER LIMIT	26.6533781	191	63.666667
RA 2	LEE J-H;BRISTOWE NC;LE…	2016	RESOLVING THE PHYSICAL ORIGIN OF OCTAHEDRAL TILTING IN HALIDE PEROVSKITES	29.0855016	155	25.833333
RA 2	SEIXAS L;RODIN AS;CARV…	2016	MULTIFERROIC TWO-DIMENSIONAL MATERIALS	31.2168023	138	23.000000
RA 2	KIM TH;PUGGIONI D;YUAN…	2016	POLAR METALS BY GEOMETRIC DESIGN	19.2032497	206	34.333333
RA 2	TIAN S;ZHANG J-F;LI C;…	2019	FERROMAGNETIC VAN DER WAALS CRYSTAL VI3	42.5701445	90	30.000000
RA 2	ZHAO M;XIA Z;HUANG X;N…	2019	LI SUBSTITUENT TUNING OF LED PHOSPHORS WITH ENHANCED EFFICIENCY, TUNABLE PHOTOLUMINESCENCE, AND IMPROVED THERMAL STABILITY	29.1937022	121	40.333333
RA 2	YE W;CHEN C;WANG Z;CHU…	2018	DEEP NEURAL NETWORKS FOR ACCURATE PREDICTIONS OF CRYSTAL STABILITY	24.0021775	130	32.500000
RA 2	BEECHER AN;SEMONIN OE;…	2016	DIRECT OBSERVATION OF DYNAMIC SYMMETRY BREAKING ABOVE ROOM TEMPERATURE IN METHYLAMMONIUM LEAD IODIDE PEROVSKITE	17.0375223	173	28.833333
Research Area 3: RA 3 (n = 477, density =0.41)
RA 3	PAGANI A;DE MIGUEL AG;…	2016	ANALYSIS OF LAMINATED BEAMS VIA UNIFIED FORMULATION AND LEGENDRE POLYNOMIAL EXPANSIONS	7.1534837	77	12.833333
RA 3	PAGANI A;CARRERA E	2017	LARGE-DEFLECTION AND POST-BUCKLING ANALYSES OF LAMINATED COMPOSITE BEAMS BY CARRERA UNIFIED FORMULATION	3.0918162	109	21.800000
RA 3	PAGANI A;CARRERA E	2018	UNIFIED FORMULATION OF GEOMETRICALLY NONLINEAR REFINED BEAM THEORIES	3.0823137	97	24.250000
RA 3	CARRERA E;DE MIGUEL AG…	2017	HIERARCHICAL THEORIES OF STRUCTURES BASED ON LEGENDRE POLYNOMIAL EXPANSIONS WITH FINITE ELEMENT APPLICATIONS	6.0912697	49	9.800000
RA 3	NEJAD MZ;HADI A	2016	NON-LOCAL ANALYSIS OF FREE VIBRATION OF BI-DIRECTIONAL FUNCTIONALLY GRADED EULER-BERNOULLI NANO-BEAMS	1.6356711	169	28.166667
RA 3	NEJAD MZ;HADI A;RASTGOO A	2016	BUCKLING ANALYSIS OF ARBITRARY TWO-DIRECTIONAL FUNCTIONALLY GRADED EULER-BERNOULLI NANO-BEAMS BASED ON NONLOCAL ELASTICITY…	1.1727529	220	36.666667
RA 3	DAN M;PAGANI A;CARRERA E	2016	FREE VIBRATION ANALYSIS OF SIMPLY SUPPORTED BEAMS WITH SOLID AND THIN-WALLED CROSS-SECTIONS USING HIGHER-ORDER THEORIES BA…	7.5675455	34	5.666667
RA 3	YAN Y;PAGANI A;CARRERA E	2017	EXACT SOLUTIONS FOR FREE VIBRATION ANALYSIS OF LAMINATED, BOX AND SANDWICH BEAMS BY REFINED LAYER-WISE THEORY	8.1243500	31	6.200000
RA 3	XU X;FALLAHI N;YANG H	2020	EFFICIENT CUF-BASED FEM ANALYSIS OF THIN-WALL STRUCTURES WITH LAGRANGE POLYNOMIAL EXPANSION	4.9756137	41	20.500000
RA 3	FILIPPI M;CARRERA E	2016	BENDING AND VIBRATIONS ANALYSES OF LAMINATED BEAMS BY USING A ZIG-ZAG-LAYER-WISE THEORY	4.5267744	45	7.500000
Research Area 4: RA 4 (n = 458, density =0.31)
RA 4	JI J-M;ZHOU H;KIM HK	2018	RATIONAL DESIGN CRITERIA FOR D-Π-A STRUCTURED ORGANIC AND PORPHYRIN SENSITIZERS FOR HIGHLY EFFICIENT DYE-SENSITIZED SOLAR …	4.0734215	169	42.250000
RA 4	JI J-M;ZHOU H;EOM YK;K…	2020	14.2% EFFICIENCY DYE-SENSITIZED SOLAR CELLS BY CO-SENSITIZING NOVEL THIENO[3,2-B]INDOLE-BASED ORGANIC DYES WITH A PROMISIN…	4.4883505	129	64.500000
RA 4	TINGARE YS;VINH NS;CHO…	2017	NEW ACETYLENE-BRIDGED 9,10-CONJUGATED ANTHRACENE SENSITIZERS: APPLICATION IN OUTDOOR AND INDOOR DYE-SENSITIZED SOLAR CELLS	5.1872676	105	21.000000
RA 4	WU W;MAO D;HU F;XU S;C…	2017	A HIGHLY EFFICIENT AND PHOTOSTABLE PHOTOSENSITIZER WITH NEAR-INFRARED AGGREGATION-INDUCED EMISSION FOR IMAGE-GUIDED PHOTOD…	1.9815177	264	52.800000
RA 4	SONG H;LIU Q;XIE Y	2018	PORPHYRIN-SENSITIZED SOLAR CELLS: SYSTEMATIC MOLECULAR OPTIMIZATION, COADSORPTION AND COSENSITIZATION	4.5038955	113	28.250000
RA 4	ZHANG A;LI C;YANG F;ZH…	2017	AN ELECTRON ACCEPTOR WITH PORPHYRIN AND PERYLENE BISIMIDES FOR EFFICIENT NON-FULLERENE SOLAR CELLS	1.7103103	209	41.800000
RA 4	WANG C-L;ZHANG M;HSIAO…	2016	PORPHYRINS BEARING A CONSOLIDATED ANTHRYL DONOR WITH DUAL FUNCTIONS FOR EFFICIENT DYE-SENSITIZED SOLAR CELLS	6.9432504	50	8.333333
RA 4	LI C;LUO L;WU D;JIANG …	2016	PORPHYRINS WITH INTENSE ABSORPTIVITY: HIGHLY EFFICIENT SENSITIZERS WITH A PHOTOVOLTAIC EFFICIENCY OF UP TO 10.7% WITHOUT A…	5.9730554	49	8.166667
RA 4	LIU Y-C;CHOU H-H;HO F-…	2016	A FEASIBLE SCALABLE PORPHYRIN DYE FOR DYE-SENSITIZED SOLAR CELLS UNDER ONE SUN AND DIM LIGHT ENVIRONMENTS	3.9554411	72	12.000000
RA 4	DI CARLO G;BIROLI AO;T…	2018	Β-SUBSTITUTED ZNII PORPHYRINS AS DYES FOR DSSC: A POSSIBLE APPROACH TO PHOTOVOLTAIC WINDOWS	4.1969495	59	14.750000
Research Area 5: RA 5 (n = 235, density =0.39)
RA 5	KURUMISAWA Y;HIGASHINO…	2019	RENAISSANCE OF FUSED PORPHYRINS: SUBSTITUTED METHYLENE-BRIDGED THIOPHENE-FUSED STRATEGY FOR HIGH-PERFORMANCE DYE-SENSITIZE…	2.4357164	125	41.666667
RA 5	HIGASHINO T;KAWAMOTO K…	2016	EFFECTS OF BULKY SUBSTITUENTS OF PUSH-PULL PORPHYRINS ON PHOTOVOLTAIC PROPERTIES OF DYE-SENSITIZED SOLAR CELLS	4.2394464	51	8.500000
RA 5	LU Y;SONG H;LI X;ÅGREN…	2019	MULTIPLY WRAPPED PORPHYRIN DYES WITH A PHENOTHIAZINE DONOR: A HIGH EFFICIENCY OF 11.7% ACHIEVED THROUGH A SYNERGETIC COADS…	2.4822110	66	22.000000
RA 5	KLFOUT H;STEWART A;ELK…	2017	BODIPYS FOR DYE-SENSITIZED SOLAR CELLS	1.5589305	97	19.400000
RA 5	YANG G;TANG Y;LI X;ÅGR…	2017	EFFICIENT SOLAR CELLS BASED ON PORPHYRIN DYES WITH FLEXIBLE CHAINS ATTACHED TO THE AUXILIARY BENZOTHIADIAZOLE ACCEPTOR: SU…	2.0185328	66	13.200000
RA 5	REDDY KSK;CHEN Y-C;WU …	2018	COSENSITIZATION OF STRUCTURALLY SIMPLE PORPHYRIN AND ANTHRACENE-BASED DYE FOR DYE-SENSITIZED SOLAR CELLS	2.6874125	47	11.750000
RA 5	WU W;MAO D;XU S;KENRY;…	2018	POLYMERIZATION-ENHANCED PHOTOSENSITIZATION	0.9257428	129	32.250000
RA 5	KRISHNA NV;KRISHNA JVS…	2017	DONOR-Π-ACCEPTOR BASED STABLE PORPHYRIN SENSITIZERS FOR DYE-SENSITIZED SOLAR CELLS: EFFECT OF Π-CONJUGATED SPACERS	1.3656442	84	16.800000
RA 5	ZENG K;CHEN Y;ZHU W-H;…	2020	EFFICIENT SOLAR CELLS BASED ON CONCERTED COMPANION DYES CONTAINING TWO COMPLEMENTARY COMPONENTS: AN ALTERNATIVE APPROACH F…	1.1464365	96	48.000000
RA 5	YANG Y;WANG L;CAO H;LI…	2019	PHOTODYNAMIC THERAPY WITH LIPOSOMES ENCAPSULATING PHOTOSENSITIZERS WITH AGGREGATION-INDUCED EMISSION	1.1281254	87	29.000000
Research Area 6: RA 6 (n = NA, density =NA)
NA	GONNISSEN J;BATUK D;NA…	2016	DIRECT OBSERVATION OF FERROELECTRIC DOMAIN WALLS IN LINBO3: WALL-MEANDERS, KINKS, AND LOCAL ELECTRIC CHARGES	4.3594863	54	9.000000
NA	PAILLARD C;BAI X;INFAN…	2016	PHOTOVOLTAICS WITH FERROELECTRICS: CURRENT STATUS AND BEYOND	0.8081700	208	34.666667
NA	DAS S;TANG YL;HONG Z;G…	2019	OBSERVATION OF ROOM-TEMPERATURE POLAR SKYRMIONS	0.3433380	225	75.000000
NA	ZUBKO P;WOJDEL JC;HADJ…	2016	NEGATIVE CAPACITANCE IN MULTIDOMAIN FERROELECTRIC SUPERLATTICES	0.3668593	210	35.000000
NA	NATAF GF;GUENNOU M;KRE…	2017	CONTROL OF SURFACE POTENTIAL AT POLAR DOMAIN WALLS IN A NONPOLAR OXIDE	4.9315838	15	3.000000
NA	SALJE EKH;ALEXE M;KUST…	2016	DIRECT OBSERVATION OF POLAR TWEED IN LAALO3	1.7404915	39	6.500000
NA	YADAV AK;NGUYEN KX;HON…	2019	SPATIALLY RESOLVED STEADY-STATE NEGATIVE CAPACITANCE	0.4600869	139	46.333333
NA	DAMODARAN AR;CLARKSON …	2017	PHASE COEXISTENCE AND ELECTRIC-FIELD CONTROL OF TOROIDAL ORDER IN OXIDE SUPERLATTICES	0.5528578	104	20.800000
NA	PORCARELLI L;ABOUDZADE…	2017	SINGLE-ION TRIBLOCK COPOLYMER ELECTROLYTES BASED ON POLY(ETHYLENE OXIDE) AND METHACRYLIC SULFONAMIDE BLOCKS FOR LITHIUM ME…	0.4962928	80	16.000000
NA	NATAF GF;GUENNOU M	2020	OPTICAL STUDIES OF FERROELECTRIC AND FERROELASTIC DOMAIN WALLS	2.0081678	18	9.000000

Development

Connectivity between the research areas

Technical description

In a bibliographic coupling network, the coupling-strength between publications is determined by the number of commonly cited references they share, assuming a common pool of references to indicate similarity in context, methods, or theory. Formally, the strength of the relationship between a publication pair \(i\) and \(j\) (\(s_{i,j}^{bib}\)) is expressed by the number of commonly cited references.

\[s_{i,j}^{bib} = \sum_m c_{i,m} c_{j,m}\]

Since our corpus contains publications which differ strongly in terms of the number of cited references, we normalize the coupling strength by the Jaccard similarity coefficient. Here, we weight the intercept of two publications’ bibliography (shared refeences) by their union (number of all references cited by either \(i\) or \(j\)). It is bounded between zero and one, where one indicates the two publications to have an identical bibliography, and zero that they do not share any cited reference. Thereby, we prevent publications from having high coupling strength due to a large bibliography (e.g., literature surveys).

\[S_{i,j}^{jac-bib} =\frac{C(i \cap j)}{C(i \cup j)} = \frac{s_{i,j}^{bib}}{c_i + c_j - s_{i,j}^{bib}}\]

More recent articles have a higher pool of possible references to co-cite to, hence they are more likely to be coupled. Consequently, bibliographic coupling represents a forward looking measure, and the method of choice to identify the current knowledge frontier at the point of analysis.

Knowledge Bases, Research Areas & Topics Interaction

Endnotes

All results are preliminary so far…